The present invention relates to an electrolytic cell and the method by which the anode support means are affixed to the interior surface of the cell. More specifically, the invention relates to a technique for affixing, in a precise manner, anode support rods to a wall or base surface of the interior cell lining by a technique that allows precise placement, eliminates leakage problems and permits the easy replacement of the anode support rod for maintenance purposes.
Electrolysis of alkali metal halide brines have been performed in mercury, diaphragm and membrane cells. These cells consist of anodes, cathodes, and may have separate anode and cathode chambers depending upon the configuration of the cell employed. Diaphragm cells, used in the electrolysis of metal halide brines, generally employ a foraminous metallic cathode and a fluid permeable diaphragm overlaying the cathode which permits the hydraulic flow of electrolyte from the anode chamber through the diaphragm into the cathode chamber. The diaphragm cells most widely used today are of the circulating electrolyte type in which the cathodes, anodes and associated diaphragms are arranged vertically and allow for easy electrolyte flow.
In the early development of electrolytic cells, the anode was constructed of a sheet of graphite and was embedded into the base of the cell through the use of molten lead, and insulated with asphalt. The disadvantages of graphite anodes are well known to those skilled in the art and will not be discussed herein.
The advent of metallic anodes with an electro-conductive coating has led to the design and operation of new configurations of cell construction. Currently, many electrolytic cells position the anodes in a vertical position and construct the anodes of a planar design and position them within the confines of the cell by attaching them to support posts or rods rising from the base of the cell. The anodes are usually of a foraminous nature and require precise positioning relative to the cathode structure within the cell. These foraminous sheets are usually bolted or clamped to the vertical anodes support rod. The positioning of these anode support rods to the base of the cell must be precise and firmly attached so that the later positioning of the anode sheets can be easily accomplished. This type of construction is illustrated in U.S. Pat. No. 3,859,196 as well as in U.S. Pat. No. 3,591,453 which illustrate the current state of the art.
Alternatively the electrolytic cell may be designed in a manner, whereby the anode support rods may be attached to a side wall of the cell, rather than to the cell base. Therefore, the term "cell wall" used in this disclosure shall encompass any of the surfaces that form the retaining outline of an electrolytic cell.
Electrical contact must be made between the applied power source and the anode in the cell. This has been accomplished in the prior art by extending the rod through the cell wall and attaching the electrical feed at the end of the anode support rod that is exposed. This electrical feed system generally employs heavy busbars due to the high current flow through the cell. The anode support rods and busbars must be constructed of a highly conductive material in order that the resistance to current flow be reduced to as small a level as possible.
In modern diaphragm type cells, the base is composed of a steel plate to provide the physical strength for the cell, and also to protect the busbar structure from corrosive attack of the electrolyte. The steel is normally protected from electrolyte attack by placing between the steel and the electrolyte, a protective layer. This protective layer has been of a flexible non-corrosive rubber type material, or in more recent applications, of a metallic sheet composed of a metal or alloys which are resistant to attack of the electrolyte used in the cell. A common type of metallic protective barrier for chloralkali cells has been the use of a titanium sheet which withstands the corrosive attack. The previous types of protective layers such as flexible rubber type sheets, fastened to the base or wall of the cell, created problems in leakage of the electrolyte to the surfaces requiring protection through the openings in the rubber sheet wherein the anode post or riser extended through the base of the cell. The replacement of these rubber-like sheets with a thin layer of a non-reactive metal, such as titanium, has allowed the cell designers to prepare better leak proof cells. In addition, the incorporation of the metallic sheet allows the welding of components to the inner surface of the cell.
The positioning of the anode support rods in an electrolytic cell must be done with precision, and the technique of attaching these rods to the wall or base of the cell has been accomplished by several techniques. A common approach has been to provide an opening through the base of the cell and to bolt the anode support rod to the base of the cell, and in so doing, provide contact with the busbar structure located near the base of the cell. This method of fastening the anode support rod to the base has produced problems which include leakage of electrolyte from the cell around the opening, and retaining the rod in its initial position after operation of the cell due to the corrosion. Other techniques for fastening anodes or anode support rods to the base of the cell have been through other simple bolting operations, and through the use of bolted guides and clips. These are described in U.S. Pat. Nos. 3,591,483; 3,719,578; and 3,796,648, which illustrate the current state of the art.